Valve timing control apparatus

ABSTRACT

A check valve is provided in a fluid passage between a phase change valve and a fluid supply source. The check valve enables a flow of the hydraulic fluid from the fluid supply source to a retarding chamber or an advancing chamber defined in a housing in corporation with a vane rotor received therein. The check valve blocks a flow of the hydraulic fluid from the retarding chamber or the advancing chamber to a fluid supply source side. A filter is provided in the fluid passage between the check valve and the fluid supply source to remove debris from the hydraulic fluid before supplying of the hydraulic fluid to the check valve.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2007-243509 filed on Sep. 20, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve timing control apparatus, which controls opening and closing timing (hereinafter, simply referred to as valve timing) of at least one of an intake valve and an exhaust valve of an internal combustion engine.

2. Description of Related Art

A previously known valve timing control apparatus includes a housing and a vane rotor (see, for example, Japanese Unexamined Patent Publication No. 2006-46315 corresponding to U.S. Pat. No. 7,182,052). The housing receives a drive force of a crankshaft of an internal combustion engine, and the vane rotor is received in the housing and transmits the drive force of the crankshaft to a camshaft. The vane rotor is rotated relative to the housing in a retarding direction or an advancing direction by controlling a pressure of hydraulic oil in retarding chambers and a pressure of hydraulic oil in advancing chambers, so that a phase of the camshaft relative to the crankshaft, i.e., valve timing is adjusted.

When intake valves or exhaust valves are driven to open and close by the valve timing control apparatus, fluctuating forces applied from the intake valves or the exhaust valves are conducted to the vane rotor, so that the torque change (torque fluctuation) is exerted in the vane rotor relative to the housing.

In a case where the hydraulic oil is supplied to the advancing chambers to change the phase of the camshaft relative to the crankshaft from the retarding side to a target phase on the advancing side, when the torque change is applied to the vane rotor toward the retarding side, the vane rotor receives the torque change in a direction for reducing a volume of each advancing chamber. Thus, the hydraulic oil in each advancing chamber receives the force, which drives the hydraulic oil out of the advancing chamber. Then, the vane rotor is returned to the retarding side by the torque change, and thereby a response time period, which is required to reach the target phase, is disadvantageously lengthened. This disadvantage becomes particularly prominent when the pressure of the hydraulic oil supplied from the oil pump is low.

In view of the above disadvantage, it has been studied to provide a check valve in an oil passage extending from a phase change valve, which supplies the hydraulic oil, to the retarding chambers and the advancing chambers to block the outflow of the hydraulic oil from the retarding chambers and the advancing chambers toward the oil pump even upon application of the torque change to the vane rotor. However, when the check valve is provided in the oil passage extending from the phase change valve to the retarding chambers and the advancing chambers, it is required to provide an oil passage and a change valve for discharging the hydraulic oil from the retarding chambers and the advancing chambers. Therefore, the construction of the oil passages becomes complicated.

Furthermore, it is conceivable to provide a check valve in an oil passage, which is present between the phase change valve and the oil pump to provide the hydraulic oil to the retarding chambers and the advancing chambers, to block the outflow of the hydraulic oil from the retarding chambers and the advancing chambers toward the oil pump even upon application of the torque change to the vane rotor, like in the case of Japanese Unexamined Patent Publication No. 2004-100523.

However, when debris (e.g., burrs detached from the interior of the internal combustion engine, abrasive powders generated by abrasion of slidable members) is mixed into the hydraulic oil, the debris may possibly be clogged in the check valve to interfere the proper function of the check valve for blocking the flow of the hydraulic oil and thereby to disable the blocking of the outflow of the hydraulic oil from the retarding chambers and the advancing chambers toward the oil pump unless the debris is reliably removed from the hydraulic oil.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a valve timing control apparatus, which has a check valve and limits intrusion of debris mixed in hydraulic fluid into the check valve while implementing relatively good response in a phase control operation toward an advancing side or a retarding side regardless of a degree of torque change.

To achieve the objective of the present invention, there is provided a valve timing control apparatus that adjusts opening and closing timing of at least one of an intake valve and an exhaust valve of an internal combustion engine and is placed in a drive force transmission system, which transmits a drive force from a drive shaft of the internal combustion engine to a driven shaft that drives the at least one of the intake valve and the exhaust valve to open and close the same. The valve timing control apparatus includes a housing, a vane rotor, a phase change valve, a check valve and a filter. The housing is rotated together with one of the drive shaft and the driven shaft and has a receiving chamber, which is formed within a predetermined angular range in a rotational direction. The vane rotor is rotated together with the other one of the drive shaft and the driven shaft and has a vane, which is received in the receiving chamber to partition the receiving chamber into a retarding chamber and an advancing chamber. The vane rotor is rotated relative to the housing in a retarding direction or an advancing direction through use of a pressure of hydraulic fluid in the retarding chamber and a pressure of hydraulic fluid in the advancing chamber to control a relative phase of the vane rotor relative the housing. The phase change valve is changeable between an operational state for supplying hydraulic fluid from a fluid supply source to the retarding chamber and an operational state for discharging the hydraulic fluid from the retarding chamber and is also changeable between an operational state for supplying the hydraulic fluid from the fluid supply source to the advancing chamber and an operational state for discharging the hydraulic fluid from the advancing chamber. The check valve is provided in a fluid passage between the phase change valve and the fluid supply source. The check valve enables a flow of the hydraulic fluid from the fluid supply source to the retarding chamber or the advancing chamber and blocks a flow of the hydraulic fluid from the retarding chamber or the advancing chamber to a fluid supply source side. The filter is provided in the fluid passage between the check valve and the fluid supply source to remove debris from the hydraulic fluid before supplying of the hydraulic fluid to the check valve.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a structural diagram showing a retarding control state of a valve timing control apparatus according to an embodiment of the present invention;

FIG. 2 is a cross sectional view taken along line II-II in FIG. 1;

FIG. 3 is a structural diagram showing an advancing control state of the valve timing control apparatus according to the embodiment;

FIG. 4A is a plan view of a check valve of the valve timing control apparatus;

FIG. 4B is a cross sectional view taken along line IVB-IVB in FIG. 4A;

FIG. 5 is a structural diagram showing the retarding control state of the valve timing control apparatus according to the embodiment;

FIG. 6 is a structural diagram showing the advancing control state of the valve timing control apparatus according to the embodiment; and

FIG. 7 is a diagram illustrating a difference between response of the valve timing control apparatus having the check valve and a filter and a previously proposed valve timing control apparatus without the check valve and the filter.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 6 show a valve timing control apparatus according to an embodiment of the present invention. The valve timing control apparatus 1 of the present embodiment is of a hydraulically controlled type that uses hydraulic oil as working fluid (hydraulic fluid) and controls valve timing of intake valves. FIG. 1 shows an operational state, in which a vane rotor 30 is driven relative to a housing 10 in a retarding direction. FIG. 3 shows another operational state, in which the vane rotor 30 is driven relative to the housing 10 in an advancing direction. FIG. 5 shows a state, in which the vane rotor 30 is driven relative to the housing 10 in the retarding direction and in which a check valve limits a leak flow of the hydraulic oil from retarding chambers to a fluid supply source. FIG. 6 shows a state, in which the vane rotor 30 is driven relative to the housing 10 in the advancing direction and in which the check valve limits the leak flow of the hydraulic oil from advancing chambers to the fluid supply source.

First, the mechanical structure of the valve timing control apparatus 1 will be described with reference to FIGS. 1 and 2. The valve timing control apparatus 1 of the present embodiment includes the housing 10, the vane rotor 30, a phase change valve 60, a check valve 80 and a filter 52. As shown in FIG. 1, the housing 10, which serves as a driving-side rotator; includes a chain sprocket 11 and a shoe housing 12. The shoe housing 12 includes a plurality of shoes 121-123 (see FIG. 2), annular peripheral wall 124 and a front plate 125, which are formed integrally. The shoes 121-123 serve as partitioning members, respectively. The front plate 125 is located on the opposite side of the peripheral wall 124, which is opposite from the chain sprocket 11. The shoe housing 12 is coaxially fixed to the chain sprocket 11 with bolts 13. The chain sprocket 11 is coupled with the undepicted crankshaft (serving as a drive shaft of the internal combustion engine) through an undepicted chain to receive a drive force therefrom and is thereby rotated together with the crankshaft.

The drive force of the crankshaft is transmitted to a camshaft (serving as a driven shaft) 3 through the valve timing control apparatus 1 to drive the intake valves (not shown). The camshaft 3 is received in the chain sprocket 11 in such a manner that the camshaft 3 and the chain sprocket 11 are driven to rotate together by the drive force transmitted from the crankshaft to the chain sprocket 11 while the camshaft 3 is rotatable relative to the chain sprocket 11 within a predetermined range of a phase difference at the time of changing the phase difference of the camshaft 3 relative to the chain sprocket 11 and thereby to the crankshaft.

The vane rotor (serving as a driven-side rotator) 30 contacts an axial end surface of the camshaft 3. The camshaft 3, the vane rotor 30 and a bush 14 are coaxially and securely joined together with a bolt 15. The positioning between the vane rotor 30 and the camshaft 3 in the rotational direction is implemented by fitting a positioning pin 16 into the vane rotor 30 and the camshaft 3. The camshaft 3, the housing 10 and the vane rotor 30 are rotated in the clockwise direction when they are seen in a direction of an arrow X in FIG. 1. Hereinafter, this rotational direction will be referred to as an advancing direction of the camshaft 3 relative to the crankshaft.

As shown in FIG. 2, the shoes 121-123, each of which is formed into a trapezoidal shape, extend radially inward from the peripheral wall 124 and are placed one after another at generally equal intervals in the rotational direction of the peripheral wall 124. The shoes 121-123 define three spaces, each of which extends a predetermined angular range in the rotational direction. These three spaces respectively form fan shaped receiving chambers 40, which receive vanes 131-133.

The vane rotor 30 includes a boss 134 and the vanes 131-133. The boss 134 is joined with the camshaft 3 at the axial end surface thereof. The vanes 131-133 are provided at the outer peripheral part of the boss 134 one after another at generally equal intervals in the rotational direction. The vane rotor 30 is received in the housing 10 in the rotatable manner relative to the housing 10. The vanes 131-133 are rotatably received in the receiving chambers 40, respectively. Each vane 131-133 divides, i.e., partitions the corresponding receiving chamber 40 into a retarding chamber and an advancing chamber. Arrows of FIG. 2, which indicate a retarding direction and an advancing direction, respectively, show the retarding direction and the advancing direction of the vane rotor 30 relative to the housing 10.

Seal members 17 are provided in slide gaps, formed between the respective shoes 121-123 and the boss 134 and between the respective vanes 131-133 and the peripheral wall 124. The seal members 17 are fitted into the grooves, which are provided in the outer peripheral wall of the boss 134 and in the outer peripheral wall of the respective vanes 131-133. Furthermore, the seal members 17 are urged by, for example, springs, toward the inner peripheral wall of the respective shoes 121-123 and the inner peripheral wail of the peripheral wall 124. With the above construction, the seal members 17 limit the leakage of the hydraulic oil between each retarding chamber and the adjacent advancing chamber.

As shown in FIG. 1, a cylindrical guide ring 18 is press fitted into a corresponding hole of the vane 131. A cylindrical stopper pin 19 is axially slidably received in the guide ring 18 in the direction of the rotational axis. An engaging ring 20 is press fitted into and is held in a recess 126, which is formed in the front plate 125. The stopper pin 19 can be fitted, i.e., engaged into the engaging ring 20. The engaging side of the stopper pin 19 and the engaging side of the engaging ring 20, which are engaged with each other, are tapered, so that the stopper pin 19 can be smoothly engaged into the engaging ring 20. A spring 21, which serves as an urging means, urges the stopper pin 19 toward the engaging ring 20 side. The stopper pin 19, the engaging ring 20 and the spring 21 form an arresting means for arresting the vane rotor 30 relative to the housing 10.

A hydraulic pressure chamber 22 is formed on a front plate 125 side of the stopper pin 19, and a hydraulic pressure chamber 23 is formed at radially outward of the stopper pin 19. The pressure of the hydraulic oil, which is supplied to the hydraulic pressure chamber 22 and to the hydraulic pressure chamber 23, acts in a direction of removing the stopper pin 19 from the engaging ring 20. The hydraulic pressure chamber 22 is connected to an advancing chamber 45 described latter, and the hydraulic pressure chamber 23 is connected to a retarding chamber 41 described latter. A distal end portion of the stopper pin 19 is engageable with the engaging ring 20 when the vane rotor 30 is placed into a most retarded position relative to the housing 10. In the state where the stopper pin 19 is engaged into the engaging ring 20, the relative rotation of the vane rotor 30 relative to the housing 10 is arrested.

When the vane rotor 30 is rotated from the most retarded position toward the advancing side, the stopper pin 19 and the engaging ring 20 are displaced from each other in the rotational direction, so that the stopper pin 19 cannot be engaged into the engaging ring 20.

As shown in FIG. 2, the retarding chamber 41 is formed between the shoe 121 and the vane 131, and a retarding chamber 42 is formed between the shoe 122 and the vane 132. Furthermore, a retarding chamber 43 is formed between the shoe 123 and the vane 133. Furthermore, an advancing chamber 45 is formed between the shoe 123 and the vane 131, and an advancing chamber 46 is formed between the shoe 121 and the vane 132. Also, an advancing chamber 47 is formed between the shoe 122 and the vane 133.

Next, the construction of the oil passages of the valve timing control apparatus 1 will be described with reference to FIGS. 1 to 4.

As shown in FIG. 1, an oil pump (a fluid supply source) 50 takes the hydraulic oil from an oil pan 51 and supplies it to a lubricating system of the internal combustion engine. A supply passage 203 supplies the hydraulic oil received from the oil pan 51 to the valve timing control apparatus 1. One end of the supply passage 203 is connected to a connecting point 201 of a branch passage 205, which supplies the hydraulic oil to the lubricating system of the internal combustion engine other than the valve timing control apparatus 1. The other end of the supply passage 203 is connected to the filter 52. The filter 52 is provided between the supply passage 203 and a supply passage 204 and includes a fine mesh 521, which filters debris (foreign objects) contained in the hydraulic oil that is supplied only to the valve timing control apparatus 1. One end of the supply passage 204 is connected to the filter 52, and the other end of the supply passage 204 is connected to the check valve 80.

The check valve 80 is provided in the supply passages 204, 207 located between the oil pump 50 and the phase change valve 60. As shown in FIGS. 4A and 4B, the check valve 80 includes a case 87, guide 84, a valve element 81 and a spring 83. The case 87 has a valve passage 89 and a valve seat 82. The valve passage 89 connects between the supply passage 204 and the supply passage 207. The valve element 81 is seatable against the valve seat 82. The valve element 81 is configured into a spherical body and is received in the valve passage 89 such that the valve element 81 is reciprocally movable in an axial direction of the case 87. The spring 83 is a compression coil spring and is received in the valve passage 89. One end of the spring 83 is in contact with the valve element 81, and the other end of the spring 83 is in contact with the guide 84. The guide 84 is received in the valve passage 89. A triple-forked portion 86 and a contacting portion 85 are formed integrally in the guide 84. The triple-forked portion 86 holds the other end of the spring 83. The contacting portion 85 guides movement of the valve element 81.

In the check valve 80, as indicated by a solid line in FIG. 4B, the valve element 81 is seated against the valve seat 82 to close the valve passage 89 when a sum of the hydraulic pressure of the hydraulic oil in the supply passage 207 and an urging force of the spring 83 per unit area is equal to or higher than the hydraulic pressure of the hydraulic oil in the supply passage 204. In contrast, as indicated by a dot-dot-dash line in FIG. 4B, the valve element 81 is lifted away from the valve seat 82 against the urging force of the spring 83 when the hydraulic pressure of the hydraulic oil in the supply passage 204 is larger than the sum of the hydraulic pressure of the hydraulic oil in the supply passage 207 and the urging force of the spring 83 per unit area.

As shown in FIG. 1, one end of the supply passage 207 is connected to the check valve 80, and the other end of the supply passage 207 is connected to an opening 73 of the phase change valve 60. The supply passages 203, 204, 207 are dedicated fluid passages, which supply the hydraulic oil only to the valve timing control apparatus 1 and are not connected to any other connecting point.

One end of a discharge passage 208 is connected to an opening 74 of the phase change valve 60, and the other end of the discharge passage 208 is connected to the oil pan 51. One end of a discharge passage 206 (FIG. 3) is connected to an opening 72 of the phase change valve 60, and the other end of the discharge passage 206 is connected to the oil pan 51. The discharge passages 208, 206 are constructed to discharge the hydraulic oil to the oil pan 51.

The phase change valve 60 is a solenoid spool valve and is connected to the supply passage 207, the discharge passages 206, 208, a retarding passage 210 and an advancing passage 220. Also, the phase change valve 60 is located on an oil pump 50 side of a bearing 2. A solenoid drive arrangement 61 of the phase change valve 60 includes a yoke 62, a stationary core 63, a movable core 64 and a coil 65. The yoke 62, the stationary core 63 and the movable core 64 are made of a magnetic material and form a magnetic circuit. When the coil 65 is energized, the coil 65 generates a magnetic flux, which passes through the magnetic circuit The coil 65 is electrically connected to an electronic control unit (ECU) 79. The ECU 79 controls the energization of the coil 65 to change a magnetic attractive force, which is generated between the stationary core 63 and the movable core 64, to drive the movable core 64.

A valve arrangement 66 of the phase change valve 60 includes a sleeve 67 and a spool 68. The openings 70-74 are formed in predetermined locations of the sleeve 67 to conduct the hydraulic oil. More specifically the opening 73 is connected to the supply passage 207, and the openings 72, 74 are connected to the discharge passage 206 (FIG. 3) and the discharge passage 208, respectively. Furthermore, the opening 71 is connected to the retarding passage 210, and the opening 70 is connected to the advancing passage 220. The spool 68 is axially reciprocally movably supported by an inner peripheral wall of the sleeve 67. Lands 75, 76 of the spool 68, each of which has an outer diameter generally equal to an inner diameter of the sleeve 67 slidably engages the inner peripheral wall of the sleeve 67. An end surface of the spool 68, which is opposite from the movable core 64, contacts the spring 69, which urges the spool 68 toward the movable core 64 side. Thus, when the solenoid drive arrangement 61 reciprocally drives the movable core 64, the spool 68 reciprocates in the sleeve 67. The spool 68 is electromagnetically driven through the energization of the coil 65 of the solenoid drive arrangement 61.

FIG. 1 shows the off-state, in which the energization of the coil 65 is turned off by the ECU 79. In this state, the spool 68 is urged by the spring 69 and is thereby held in the predetermined location at the left side in FIG. 1. In this way, the hydraulic oil, which is supplied from the oil pump 50 to the supply passages 203, 204, 207, enters into the interior of the sleeve 67 through the opening 73 and is thereafter supplied to the retarding passage 210 through the opening 71. Furthermore, the hydraulic oil of the advancing passage 220 enters into the interior of the sleeve 67 through the opening 70 and is thereafter discharged from the opening 74 to the oil pan 51 through the discharge passage 208.

FIG. 3 shows the on-state, in which the energization of the coil 65 is turned on by the ECU 79 and is controlled at a predetermined duty ratio. In this state, the spool 68 is urged against the urging force of the spring 69 toward the right side in FIG. 3 and is thereafter held in a balanced position, at which the urging force of the spring 69 and the magnetic attractive force between the cores 63, 64 of the solenoid drive arrangement 61 are balanced. In this way, the hydraulic oil, which is supplied from the oil pump 50 to the supply passages 203, 204, 207, enters into the interior of the sleeve 67 through the opening 73 and is thereafter supplied to the advancing passage 220 through the opening 70. Furthermore, the hydraulic oil of the retarding passage 210 enters into the interior of the sleeve 67 through the opening 71 and is thereafter discharged from the opening 72 to the oil pan 51 through the discharge passage 206.

In another state, in which the energization of the coil 65 is turned on by the ECU 79 and is controlled at a different duty ratio that is different from that of FIG. 3, the spool 68 is urged toward the right side in FIG. 3 by the amount less than that of FIG. 3, so that the spool 68 is held in a corresponding balanced position, at which the urging force of the spring 69 and the electromagnetic force of the solenoid drive arrangement 61 are balanced. In this way, the hydraulic oil, which is supplied from the oil pump 50 to the supply passages 203, 204, 207, may enter into the interior of the sleeve 67 through the opening 73. However, at this time, the openings 71, 70 are respectively closed by the lands 75, 76, so that the flow of the above hydraulic oil to the retarding passage 210 and the advancing passage 220 is limited.

As shown in FIG. 1, annular passages 240, 242 are formed in an outer peripheral wall of the camshaft 3, which is supported by the bearing 2 of the valve timing control apparatus 1. The retarding passage 210 extends from the phase change valve 60 to the interior of the boss 134 of the vane rotor 30 through the annular passage 240 and a retarding passage 211 of the interior of the camshaft 3. Furthermore, the advancing passage 220 extends from the phase change valve 60 to the interior of the boss 134 of the vane rotor 30 through the annular passage 242 and an advancing passage 221 of the interior of the camshaft 3.

With reference to FIG. 2, the retarding passage 211 is branched into three retarding passages 243-245, which are connected to the retarding chambers 41-43, respectively. The retarding passage 210, the annular passage 240 and the retarding passages 211, 243-245 supply the hydraulic oil to the respective retarding chambers 41-43 from the supply passage 204 through the phase change valve 60 and drain the hydraulic oil from the respective retarding chambers 41-43 to the oil pan 51 side (fluid discharge side) through the phase change valve 60 and the discharge passage 206. Thus, the retarding passage 210, the annular passage 240 and the retarding passages 211, 243-245 serve as both a retarding side supply passage and a retarding side discharge passage.

The advancing passage 221 is branched into three advancing passages 246-248, which are connected to the advancing chambers 45-47, respectively. The advancing passage 220, the annular passage 242 and the advancing passages 221, 246-248 supply the hydraulic oil to the respective advancing chambers 45-47 from the supply passage 204 through the phase change valve 60 and drain the hydraulic oil from the respective advancing chambers 45-47 to the oil pan 51 side (fluid discharge side) through the phase change valve 60 and the discharge passage 208. Thus, the advancing passage 220, the annular passage 242 and the advancing passages 221, 246-248 serve as both an advancing side supply passage and an advancing side discharge passage.

Because of the above mechanical construction and the oil passages of the valve timing control apparatus 1, the check valve 80, which is provided between the supply passage 204 and the supply passage 207, limits the backflow of the hydraulic oil from the respective retarding chambers 41-43 to the oil pump 50 side through the retarding passages 243-245, 211, the annular passage 240, the retarding passage 210 and the supply passage 207 and also limits the backflow of the hydraulic oil from the respective advancing chambers 45-47 to the oil pump 50 side through the advancing passages 246-248, 221, the annular passage 242, the advancing passage 220 and the supply passage 207. Furthermore, since the check valve 80 is provided in the supply passages 204, 207, which are located on the phase change valve 60 side of the connecting point 201, the hydraulic oil, which tries to generate the backflow from the retarding chambers 41-43 or the advancing chambers 45-47, does not flow to the lubricating system of the internal combustion engine other than the valve timing control apparatus 1.

The filter 52 is provided in the supply passages 203, 204, which are located on the check valve 80 side of the connecting point 201. Thus, even when the hydraulic oil containing the debris is taken by the oil pump 50, the filter 52 can remove the debris from the hydraulic oil. Thus, supply of the debris into the check valve 80 is limited. Therefore, the one-way valve function of the check valve 80 is not interfered, so that the flow of the hydraulic oil from the phase change valve 60 to the oil pump 50 can be reliably limited. In this way, the valve timing control apparatus 1 can make the appropriate response at the time of changing the phase to the advancing side or the retarding side regardless of the degree of the torque change.

Next, the operation of the valve timing control apparatus 1 will be described with reference to FIGS. 1 and 3.

In the stop state of the internal combustion engine, the stopper pin 19 is engaged into the engaging ring 20. Right after starting of the internal combustion engine, sufficient hydraulic oil is not supplied from the oil pump 50 to the retarding chambers 41-43, the advancing chambers 45-47 and the hydraulic pressure chambers 22, 23. Thus, the stopper pin 19 is still engaged into the engaging ring 20, and the camshaft 3 is held in the most retarded position relative to the crankshaft. Therefore, the vane rotor 30 is repeatedly circumferentially swung back and forth to repeatedly hit the housing 10, resulting in generation of hammering sound due to the torque fluctuations received by the camshaft until the hydraulic oil is supplied to the respective hydraulic chambers.

When the sufficient hydraulic oil is supplied from the oil pump 50 after the starting of the internal combustion engine, the stopper pin 19 is removed from the engaging ring 20 by the hydraulic pressure of the hydraulic oil supplied to the hydraulic pressure chamber 22 or the hydraulic pressure chamber 23. Thereby, the rotor 30 can now rotate relative to the housing 10. The phase difference of the camshaft 3 relative to the crankshaft is adjusted by controlling the hydraulic pressure applied to the respective retarding chambers and the hydraulic pressure applied to the respective advancing chambers.

During the operating period of the internal combustion engine, in the state of FIG. 1 where the electric power supply to the phase change valve 60 is turned off, the spool 68 is held in the position shown in FIG. 1 by the load of the spring 69. When the phase change valve 60 is held in the state shown in FIG. 1, the hydraulic oil, which is discharged from the oil pump 50, passes through the connecting point 201 and the supply passage 203 and is supplied to the filter 52. The filter 52 removes the debris mixed into the hydraulic oil. The hydraulic oil, from which the debris is removed, is supplied from the supply passage 204 to the valve passage 89 of the check valve 80 and then passes through the supply passage 207. Thereafter, the hydraulic oil is supplied from the supply passage 207 to the interior of the sleeve 67 through the opening 73 of the phase change valve 60. At this time, the check valve 80 enables the flow of the hydraulic oil.

The hydraulic oil, which is outputted from the opening 71 of the phase change valve 60, passes through the retarding passage 210, the annular passage 240 and the retarding passages 211, 243-245 and is supplied into the retarding chambers 41-43. Furthermore, the hydraulic oil of the advancing chambers passes the advancing passages 246-248, 221, the annular passage 242, the advancing passage 220, the phase change valve 60 and the discharge passage 208 and is discharged into the oil pan 51. Thereby, the hydraulic oil is supplied to the respective retarding chambers, and the hydraulic oil is discharged from the respective advancing chambers. In this way, the vane rotor 30 receives the hydraulic pressure from the three retarding chambers 41-43, so that the vane rotor 30 is rotated relative to the housing 10 in the retarding direction.

When the electric power supply to the phase change valve 60 is turned on, the spool 68 is moved to the position show in FIG. 3 by the electromagnetic force of the solenoid drive arrangement 61, which is exerted against the load of the spring 69. When the phase change valve 60 is held in the state shown in FIG. 3, the hydraulic oil, which is discharged from the oil pump 50, passes through the connecting point 201 and the supply passage 203 and is supplied to the filter 52. The filter 52 removes the debris mixed into the hydraulic oil. The hydraulic oil, from which the debris is removed, is supplied from the supply passage 204 to the valve passage 89 of the check valve 80 and then passes through the supply passage 207. Thereafter, the hydraulic oil is supplied from the supply passage 207 to the interior of the sleeve 67 through the opening 73 of the phase change valve 60. The hydraulic oil, which is outputted from the opening 70 of the phase change valve 60, passes through the advancing passage 220, the annular passage 242 and the advancing passages 221, 246-248 and is supplied into the advancing chambers 45-47. Furthermore, the hydraulic oil of the retarding chambers passes the retarding passages 243-245, 211, the annular passage 240, the retarding passage 210, the phase change valve 60 and the discharge passage 206 and is discharged into the oil pan 51. Thereby, the hydraulic oil is supplied to the respective advancing chambers, and the hydraulic oil is discharged from the respective retarding chambers. In this way, the vane rotor 30 receives the hydraulic pressure from the three advancing chambers 45-47, so that the vane rotor 30 is rotated relative to the housing 10 in the advancing direction.

When the vane rotor 30 reaches a target phase, the ECU 79 controls the duty ratio of the drive current supplied to the phase change valve 60 to hold the spool 68 in an intermediate position between the position of FIG. 1 and the position of FIG. 3. In this state, the hydraulic oil, which is supplied from the oil pump 50 through the supply passage 207, passes the gaps, each of which is formed between the corresponding one of the lands 75, 76 and the corresponding one of the openings 71, 70, so that the small amount of hydraulic oil is supplied to both of the retarding passage 210 and the advancing passage 220 to apply the pressure.

Next, the characteristic operation of the valve timing control apparatus 1 of the present embodiment will be described with reference to FIGS. 5 and 6.

During the operating period of the internal combustion engine, as shown in FIG. 5, at the time of phase control operation (retarding operation) for adjusting the phase to the target phase at the retarding side by supplying the hydraulic oil to the respective retarding chambers and by discharging the hydraulic oil from the respective advancing chambers, the vane rotor 30 receives the torque changes (torque fluctuation) toward the retarding side and the advancing side with respect to the housing 10 due to the torque changes (torque fluctuation) applied to the camshaft 3. When the vane rotor 30 receives the torque change toward the advancing side, the hydraulic oil in the respective retarding chambers receives the force to drive the hydraulic oil out of the retarding chambers toward the retarding passages 243-245, 211, the annular passage 240, the retarding passage 210 and the supply passage 207.

Here, in the present embodiment, the check valve 80 is provided between the supply passage 207 and the supply passage 204. Therefore, the check valve 80 closes the valve passage 89 when the sum of the hydraulic pressure of the hydraulic oil, which is applied from the respective retarding chambers to the retarding passages 243-245, 211, the annular passage 240, the retarding passage 210 and the supply passage 207, and the urging force of the spring 83 per unit area is larger than the hydraulic pressure of the hydraulic oil discharged from the oil pump 50. Thus, the hydraulic fluid does not flow out of the respective retarding chambers to the retarding passages 243-245, 211, the annular passage 240, the retarding passage 210 and the supply passage 207. The filter 52 is provided in the supply passages 203, 204 on the check valve 80 side of the connecting point 201 to limit the inflow of the debris of the hydraulic oil into the check valve 80. Therefore, the check valve 80 can reliably limit the backflow of the hydraulic oil. Therefore, in the state where the hydraulic pressure of the oil pump 50 is low, even when the vane rotor 30 receives the torque change toward the advancing side, the check valve 80 can limit the returning of the vane rotor 30 toward the advancing side relative to the housing 10. As described above, it is possible to limit the returning of the vane rotor 30 relative to the housing 10 toward the advancing side, which is opposite from the target phase. Thus, the vane rotor 30 can quickly reach the target phase at the retarding side.

As shown in FIG. 6, at the time of phase control operation (advancing operation) for adjusting the phase to the target phase at the advancing side by supplying the hydraulic oil to the respective advancing chambers and by discharging the hydraulic oil from the respective retarding chambers, the vane rotor 30 receives the torque changes (torque fluctuation) toward the retarding side and the advancing side with respect to the housing 10 due to the torque changes (torque fluctuation) applied to the camshaft 3. When the vane rotor 30 receives the torque changes toward the retarding side, the hydraulic oil in the respective advancing chambers receives the force to drive the hydraulic oil out of the advancing chambers toward the advancing passages 246-248, 221, the annular passage 242, the advancing passage 220 and the supply passage 207.

Here, in the present embodiment, the check valve 80 is provided between the supply passage 207 and the supply passage 204. Therefore, the check valve 80 closes the valve passage 89 when the sum of the hydraulic pressure of the hydraulic oil, which is applied from the respective advancing chambers to the advancing passages 246-248, 221, the annular passage 242, the advancing passage 220 and the supply passage 207, and the urging force of the spring 83 per unit area is larger than the hydraulic pressure of the hydraulic oil discharged from the oil pump 50. Thus, the hydraulic oil in the respective advancing chambers do not flow out of the advancing chambers toward the advancing passages 246-248, 221, the annular passage 242, the advancing passage 220 and the supply passage 207. The filter 52 is provided in the supply passages 203, 204 on the check valve 80 side of the connecting point 201 to limit inflow of the debris of the hydraulic oil into the check valve 80. Therefore, the check valve 80 can reliably limit the backflow of the hydraulic oil. Therefore, in the state where the hydraulic pressure of the oil pump 50 is low, even when the vane rotor 30 receives the torque change toward the retarding side, the check valve 80 can limit the returning of the vane rotor 30 toward the retarding side relative to the housing 10. As described above, it is possible to limit the returning of the vane rotor 30 relative to the housing 10 toward the retarding side, which is opposite from the target phase. Thus, the vane rotor 30 can quickly reach the target phase at the advancing side.

Even in the intermediate holding position, the small amount of hydraulic oil flows backward from both of the retarding passage 210 and the advancing passage 220 toward the supply passage 207 to apply the pressure to the check valve 80. Even in this case, the check valve 80 closes the valve passage 89 upon seating of the valve element 81 against the valve seat 82 when the sum of the hydraulic pressure of the hydraulic oil in the supply passage 207 and the urging force of the spring 83 per unit area becomes equal to or larger than the hydraulic pressure of the hydraulic oil discharged from the oil pump 50. In this way, the retarding passage 210 and the advancing passage 220 are both closed, and thereby the backflow of the hydraulic oil from the respective retarding chambers and the respective advancing chambers toward the oil pump 50 side through the retarding passage 210, the advancing passage 220 and the supply passage 207 is limited.

Now, the response of the valve timing control apparatus 1 of the present embodiment at the time of controlling the phase will be compared with that of a previously proposed valve timing control apparatus based on FIG. 7.

As indicated by a solid line Q in FIG. 7, in the valve timing control apparatus 1 of the present embodiment, the check valve 80 and the filter 52 reliably block the backflow of the hydraulic oil from the retarding chambers and the advancing chambers toward the oil pump to implement the appropriate phase control operation. Thus, the amount of return movement b of the vane rotor toward the retarding side caused by the torque change is relatively small, and the vane rotor reaches the target phase within the predetermined time period.

In contrast, in the previously proposed valve timing control apparatus, which does not have the check valve and the filter described above, the appropriate phase control operation cannot be performed. Thus, as indicated by a dotted line P in FIG. 7, the amount of return movement a of the vane rotor becomes relatively large, and thereby the vane rotor cannot reach the target phase within the predetermined time period.

As described above, in the valve timing control apparatus 1 of the present embodiment, the check valve and the filter are provided to reliably block the backflow of the hydraulic oil from the retarding chambers and the advancing chambers toward the oil pump and thereby to improve the response in the phase control operation regardless of the degree of the torque change.

In the above embodiment, the present invention is implemented in the valve timing control apparatus of the intake valves. Alternatively, the present invention may be applied to a valve timing control apparatus, which controls the exhaust valves or both of the intake valves and the exhaust valves.

Furthermore, in the present embodiment, the phase change valve of the solenoid spool valve type is used. Alternatively, a phase change valve of any other type may be used as long as the hydraulic oil from the oil pump can be switched to supply it to the retarding passage or the advancing passage while the hydraulic oil from the retarding passage or the advancing passage can be switched to discharge it into the discharge passage.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A valve timing control apparatus that adjusts opening and closing timing of at least one of an intake valve and an exhaust valve of an internal combustion engine and is placed in a drive force transmission system, which transmits a drive force from a drive shaft of the internal combustion engine to a driven shaft that drives the at least one of the intake valve and the exhaust valve to open and close the same, the valve timing control apparatus comprising: a housing that is rotated together with one of the drive shaft and the driven shaft and has a receiving chamber, which is formed within a predetermined angular range in a rotational direction; a vane rotor that is rotated together with the other one of the drive shaft and the driven shaft and has a vane, which is received in the receiving chamber to partition the receiving chamber into a retarding chamber and an advancing chamber, wherein the vane rotor is rotated relative to the housing in a retarding direction or an advancing direction through use of a pressure of hydraulic fluid in the retarding chamber and a pressure of hydraulic fluid in the advancing chamber to control a relative phase of the vane rotor relative the housing; a phase change valve that is changeable between an operational state for supplying hydraulic fluid from a fluid supply source to the retarding chamber and an operational state for discharging the hydraulic fluid from the retarding chamber and is also changeable between an operational state for supplying the hydraulic fluid from the fluid supply source to the advancing chamber and an operational state for discharging the hydraulic fluid from the advancing chamber; a check valve that is provided in a fluid passage between the phase change valve and the fluid supply source, wherein the check valve enables a flow of the hydraulic fluid from the fluid supply source to the retarding chamber or the advancing chamber and blocks a flow of the hydraulic fluid from the retarding chamber or the advancing chamber to a fluid supply source side; and a filter that is provided in the fluid passage between the check valve and the fluid supply source to remove debris from the hydraulic fluid before supplying of the hydraulic fluid to the check valve.
 2. The valve timing control apparatus according to claim 1, wherein: the fluid passage between the phase change valve and the fluid supply source includes a connecting point, which is connected to a branch passage that supplies the hydraulic fluid to a lubricating system of the internal combustion engine; and the check valve is provided in the fluid passage between the connecting portion and the phase change valve.
 3. The valve timing control apparatus according to claim 2, wherein the filter is provided in the fluid passage between the connecting point and the check valve. 